Scientists
working on the MARTE (Mars Astrobiology Research and Technology Experiment)
project have been drilling into the ground around Rio Tinto in Spain. They were studying underground environments and discovered areas that were
inhospitable to life.
Inhospitable,
that is, until they were colonized by tough
microbes.
These
organisms improved conditions so much that other creatures could move in. This
has important implications when looking for life on other planets.
Living in harmony
The
team,
led by David Fernández-Remolar of the Centro de Astrobiología in Spain, expected the underground areas to be barren. They were understandably surprised to
find places perfect for microscopic life. What was going on? The answer came in
the form
of tiny microbes that reacted with the rocks and then gave off heat. It
wasn't much — just enough to raise the overall temperature and make the
environment more liveable.
So
just by colonizing an area under the ground, the microbes made it habitable for
other forms of life. They're like construction workers, building comfortable homes
for others. Of course, the microbes weren't trying to make conditions better —
it's just a happy side-effect of their natural processes.
The
researchers also found that the acidic conditions they were expecting had been
neutralized by metals, making the water safe for life. The microbes aren't
involved in this process, although they do benefit from it.
Such
a two-tiered system could make areas on other planets relatively cosy for
simple life. It can even help us find evidence for past or present life on
Mars: We could look for slight temperature increases near the surface, or the
chemicals that reduce water acidity. Such tell-tale signs would indicate that
the same mechanisms working in Rio
Tinto could be happening on Mars.
Martian rock pools
Using
these discoveries, we can imagine how life
on Mars could have developed. Conditions on the red planet in the past were
very different from today. There was probably warm water underground, which
would have helped make certain metallic ores. These are important as they could
have been used as food for the "construction worker" microbes.
As
they grew and reacted with the rocks around them, the microbes would have
generated heat, making their environment warmer. It would have still been
bitterly cold, but salts would have kept the water liquid, even if the
temperature dipped below the freezing point. This shallow water could have
protected the microbes and any other life from the sun's normally lethal ultraviolet
radiation.
Metals
in the rocks would have made sure that the water wasn't too acidic. Over time
other organisms could have colonized the area after the first microbes had made
conditions much nicer for life. The result would have been simple Martian rock
pools teeming with strange microbial life. Looking into one such pool
with a microscope would be a dream come true for astrobiologists.
"It may be possible that the inner habitats of planets
were not only the first refuge of life, but may also have become the last for
planets such as Mars," the researchers report.
Once
our technology for studying planets around other stars improves, we could
search for signs of life like this around distant worlds. They may not be as
glamorous as aliens we could talk to, but these hard-working microbes may well
provide the foundations for areas filled with exotic life.
The research is detailed in the spring issue of the journal Astrobiology.
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